Chlorine has saved countless millions of lives and it continues to perform humane miracles to this day. But it is effective because it is indeed a killer. Not only can chlorine create carcinogens after reacting with organic compounds in water, as anybody who has dipped into a municipal swimming pool will know it does not taste or smell that nice either. Many people do not like the taste of heavily chlorinated water, making household filters and even bottled water increasingly attractive in markets such as the USA. In the background are a body of data assembled by institutions such as the US Environmental Protection Agency suggesting that too much exposure to chlorinated water is potentially harmful to for example, pregnant women. This has been grabbed with aplomb by lobbyists for every cause, but it leaves us with one great question – how do we deliver water that people can enjoy drinking and can trust, at a fair and attractive price?
Going forwards to a post chlorine drinking water takes us back to water treatment’s roots. Sand filtration is a great way of cleaning up a water stream before using UV. Slow sand filters have been used for treating water since the days of the Egyptians, with small plants used across the medieval world and for a town for the first time in Paisley in 1804. In 1829, the first large scale facility opened, serving the Chelsea waterworks company (now part of Thames Water) in 1829. During much of this time, it was assumed that diseases were transmitted by ‘miasmas’ in foul air and the sand was simply making the water more pleasant to drink.
Sometimes water engineering is a triumph of hope over reality. Leafing through the water treatment literature, you are assured that each technique will blast all bugs into oblivion, with clear sterile water coming out the other end. For example, while Ultra Violet disinfection is a powerful way of finishing off water or wastewater treatment it is only as good as the fluid that you treat and when suspended solids remain, they create a shadow behind which pathogens can survive.
Today, with our fuller understanding of infections and impurities and how to deal with them, sand filtration has much to offer when it comes to removing particulates from treated water. But sand filtration was not called ‘slow sand’ without reason. Even in modern ‘rapid sand’ units the flow rate can be low and the maintenance needs can be high.
BlueWater Bio acquired Filter Clear in 2011 to expand its range of offerings in water and wastewater treatment. Filter Clear’s forte is to minimise contaminant build up so that the units operative life is maximised, while being able to maintain a flow rate which is appreciably higher than seen in slower sand filters. Unlike sand based filtration systems, an internal self-cleaning backwash system cuts back on the downtime needed for cleaning. Even so, the system can retain particles down to 0.5 to 1.0 microns compared with 3.0-10.0 in competing technologies, which minimises the size and concentration of suspended solids remaining in the filtrate.
So, using a Filter Clear unit as a pre-treatment for UV, micro-organisms can run through the water, but they cannot hide. The process removes particulates from the water, giving the UV a free run to eliminate all the contaminants and minimising or removing the need for any post treatment chloride.
(original article by Robert Jobson, Evening Standard, 11 November 2016) Prince Charles’s state visit to the Gulf has...
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